Scariest horror movies?

I absolutely adore horror and respect the fact that I might be desentisized to being actually scared by them, as I tend to watch one every night and have done so every night. Regardless, it's my favourite genre by a good mile.

I'm still hoping for that feeling when a movie hits you in the nerve and catches you off guard, maybe even creeps into your thoughts later when you're in bed.

So I turn to you my fellow horror fans, what are the movies you have found to be the scariest?

I personally have been most moved and terrified by The Grudge 2004 remake back when I was a teen, Shutter (thai), Halloween, Blair Witch Project, The Descent, It Follows and Hereditary, so kinda everything works for me, except maybe overtly excessive gore. Gimme your best shot!